Method of producing photographic



United States Patent Ofiice 2,733,144 Patented Jan. 31, 1956 METHOD OF PRODUCg IG PHGTOGRAPHIQ Tijs Willem van Rijssel, Harlte Jan Houtman, and Hendrik Jonker, Eindhoven, Netherlands, assignors to Hartford National Bank and Trust Company, Hartford, Conn as trustee No Drawing. Application March 6, 1952, Serial No. 275,214

Claims priority, application Netherlands March 28, N51

14 Claims. (Ci. 95-6) It has been suggested to produce photographic images by providing a support with a photo-sensitive substance whose dissociation product obtained by exposure of the layer reacts with mercurous salts with the formation of mercury. The mercurous salt may be introduced into the support prior to or subsequent to the exposure. This method will be referred to hereinafter as the mercurous system.

A mercury image is thus obtained which can be stabilised and intensified by physical development with a developer containing a salt of a precious metal. The term precious metal is to be understood to mean hereinafter a metal which in the electrolytical voltage series of the metals is beyond copper or a mixture of such metals or else an alloy of such metals. In practice, silver is most suitable but in certain cases use may be made of mercury, gold and other precious metals. The precious metal images so obtained (for the sake of simplicity reference will be made hereinafter to silver images) are not inferior in quality to the silver images obtained when using initially photo-sensitive systems in which a silver halide emulsion is exposed and the latent silver image obtained is developed, and they are differentiated particularly by a very high resolving power. However, a disadvantage inherent in the mercurous system with subsequent intensification of the contrast by means of physical development is the comparatively low sensitiveness, which indeed is lower by a value 40 than the greatly varying sensitivity of silver halide-gelatine systems. Accordingly, this disadvantage inter alia renders the mercurous system less adapted for taking direct photographic exposures and for making enlargements. The very much lower photo-sensitivity of the mercurous system is most probably due inter alia to the fact that the mercury germs formed as a result of the exposure are comparatively large and thus low in number so that the subsequent physical development is much less efiicient, since the ultimate density of the silver image obtained by physical development is most intimately related to the number of developable mercury germs.

The object of the present invention is to increase the photo-sensitivity of the mercurous system by increasing the number of developable mercury germs. It might be expected that the reaction whereby these germs are formed will be assisted bythe increase in activity of the mercurous ions in the reaction zone. However, it is surprising to find that if, prior to the physical development of the latent metal image obtained by exposure (which image is in some cases already visible) to form a silver image, introduction into the photo-sensitive layer of an anion which is capable of reducing the activity of mercurous ions and which under the prevailing conditions does not form any precipitate with mercurous ions, enables the number of developable mercury germs to be increased. Although the pH-value, which must be located in the acid region in order to avoid spontaneous separation of mercury, interferes with the result it has been found that even with a constant pH-value there is an efiect of the said anions right enough. By way of illustration, reference may be had to Example IX in which the sensitivity of a foil containing a diazo compound which subsequently to exposure is after-treated with a solution containing mercurous ions and having lactate ions added to it or not respectively is compared, the pH-value being equal in both cases. The sensitivity in the case of lactate admixture is found to be three times that in the case without lactate admixture.

The reduction in activity of the mercurous ions may be due to the fact that with the anion referred to the ions form a soluble, little dissociated compound. Mercurous ions are regenerated from this compound in proportion as the free mercurous ions which are present in the liquid are consumed. As the additions most suitable for use, we may mention those of soluble lactates, acetates or citrates and/or the corresponding acids. Particularly good results are obtained by the addition of alkali lactates and/or lactic acid. It should be noted that although the increase in sensitivity enabled by the use of the invention is considerable, it is generally not yet sufiicient to render the mercurous system suitable for use in taking direct photographic exposures.

In carrying out the new method the following possibilities may be distinguished in principle:

(a) In addition to the photo-sensitive compound, at least the mercurous compound is present in the lyophile layer prior to exposure;

(1)) in addition to the photo-sensitive compound, at least the compound comprising the anion referred to is present in the lyophile layer prior to exposure;

(0) The mercurous compound and the compound comprising the anion referred to are introduced into the lyophile layer subsequently to exposure.

It is self-evident that, in all these cases, physical development is ultimately eliected with the use of a developer containing a precious metal salt.

As results from the above, use may be made of salts or of acids comprising the said anions or else of combinations of the two. It will often be preferable that in those cases in which a neutral photo-sensitive compound (for example a complex metal cyanide or a diazosulphonate) is used, the anion should be added as a free acid. However, in the case of a strong acid compound (for example a diazonium sulphonic acid) the anion will often be added in the form of an alkali salt. Naturally, the anions concerned must satisfy the condition that in an acid medium with mercurous salts they should not bring about separation of mercury, since otherwise formation of mercury, that is to say fogging, would ensue at the unexposed points.

In order that the invention may be readily carried into effect, a number of examples will now be described in detail.

Example I Superficially saponified cellulose acetate'is sensitised by soaking for 2 minutes in a 0.1 n solution of orthonitro-mandelic acid nitrile in 30% ethanol.

The foil is exposed for 60 seconds with use of a watt mercury vapour lamp.

it is then treated for 30 seconds with a solution of 0.08 n mercurous nitrate in 0.04 n nitric acid having sodium lactate added to it in a concentration of 0.08 n; subsequently development is effected for 7 minutes in a solution containing 1% metol, 4% citric acid and 0.07% silver nitrate.

The sensitivity is from 6 to 8 times greater than that when the lactate is omitted from the mercurous bath.

Example II A foil made of superficially saponified cellulose acetate is sensitised with an aqueous solution of 0.4 n hydroxy-l diazo-2 methyl-6 benzolsulphonic acid-4, 0.1 n mercurous nitrate and 0.3 n sodium lactate.

After drying the foil is exposed for 4 seconds behind a sensitometer wedge at a distance of 10 cms. from a 250 watt high-pressure mercury vapour lamp. Under these conditions the light intensity determined in the wave length region of from 3000 to 6000 A. is 600,000

ergs/square cm. per second.

The foil is then bathed in water for 1 minute and finally physically developed for 6 minutes in a developer containing 0.5% metol, 1% tartaric acid and 0.2% silver nitrate in water.

If the sensitising solution contains sodium lactate, the sensitivity is 1 X 10- whereas in the use of a sensitising solution without sodium lactate it is 3.3 X the sensitivity in the first case being consequently three times that in the second case. The sensitivity here indicated is the reciprocal of the exposure energy I X t (I expressed in er'gs/square cm. per second 2 in seconds) required to obtain a density of 0.1 (that is to say 0.05 beyond fogging). The density is measured with the use of a photoelectric cell.

Example III A foil made of regenerated cellulose is sensitised with an 0.1 n aqueous solution of the monosodium salt of diazod hydroxy-2 naphthalene bisulphonic acid-4.6, which contains in addition 0.025 n mercurous nitrate and 0.05 n nitric acid.

After drying, it is exposed for 16 seconds behind a sensitometer wedge with the use of a 250 watt high-pressure mercury vapour lamp at a distance of 10 cms. The exposed foil is then treated for one minute in a 0.6 11 sodium lacetate solution and then physically developed in the manner described in Example II.

The resultant sensitivity is greater by a value 20 than if the foil is treated with Water instead of the sodium lactate solution referred to.

Example IV A foil of superficially saponified cellulose acetate is sensitised with an aqueous solution of 0.4 n hydroxy-l diazo-2 methyl-6 benzolsulphonic acid-4, 0.025 n mercurous nitrate and 0.2 n sodium lactate.

After drying, the foil is exposed for 4 seconds behind a sensitometer wedge at a distance of 10 cms. from a 250 watt high-pressure mercury vapour lamp, then bathed for 1 minute in a 0.6 n solution of sodium lactate and finally physically developed for 6 minutes in a developer containing 0.5% metol, 2% citric acid and 0.2% silver nitrate in water.

Due to thepresence of sodium lactate in the sensitising solution and. the after-treatment bath the sensitivity is increased by a value 6.

Example V sitometer wedge with the use of a high-pressure mercury vapour lamp at a distance of 10 cms., then treated in water for 1 minute and physically developed as described in Example IV.

When the sensitising solution does not contain sodium citrate the sensitivity is lower by a value 3.

Example VI Unsize'd paper is sensitised with an aqueous solution of 0.2 n hydroxy-l .diazov2 methyl-6 benzolsulphonic acid4 and 0.05 n mercurousfnitrate.

After drying, the paper is exposed for 2 seconds behind a sensitometer wedge at a distance of 10 cms. from a high-pressure mercury vapour lamp. The exposed paper Example VII A foil of superficially saponified cellulose-acetate is sensitised with an aqueous solution of 0.4 n hydroxy-l diazo-2 benzolsulphonic acid-4 and 0.2 11 sodium lactate.

After drying, the foil is exposed for 8 seconds behind a sensitometer wedge at a distance of 10 cms. from a 250 Watt high-pressure mercury vapour lamp, then treated for 1 minute in an aqueous solution of 0.1 n mercurous nitrate and 0.5 n nitric acid and subsequently physically developed for 10 minutes in the manner described in Example IV. The increase in sensitivity due to the presence of sodium lactate in the sensitising solution is a value 2. If the exposed foil is bathed for 1 minute in an aqueous solution of 0.1 n mercurous nitrate, 0.05 n

nitric acid and 0.1 11 sodium lactate the increase in sen-' sitivity is a value 4.

If the exposed foil is physically developed for 5 minutes in a developer containing 0.5% metol, 0.1 n mercurous nitrate, 0.05 n nitric acid and 0.1 11 sodium lactate,

the sensitivity is higher by a value 2.5 than if no sodium, lactate is present in the sensitising solution and in the developer solution.

Example VIII superficially. saponified acetyl cellulose is sensitised with an aqueous solution of 0.2 n methoxy-l benzol-4 diazo sodium sulphonate.

After drying, it is exposed for /2 second behind a sensitometer wedge with the use of a 250 watt high-pressure mercury vapour lamp at a distance of 10 cms., after that it is treated for 1 minute in an aqueous solution of 0.1 n

Example IX A foil sensitised and exposed in the manner described in Example VIII is treated for 1 minute in an aqueous solution of 0.063 n mercurous nitrate, 0.45 n lactic acid I and 0.04 11 sodium lactate.

The pH-value and the pHg2++-value of this: bath is 1.86 and 3.00 respectively. Physical development is thenetfected for 10 minutes in a developer as described in Example IV.

If. the after-treatment bath. contains. only mercurous nitrate in the concentration given, the pH-value and the pHgz'value are 1.86, and 1.68 respectively and the sensitivity is lower by a value 3.v

Example X A foilof superficially saponified cellulose acetate is sensitised and exposed in.the manner described in ExampleVIII. Subsequently to exposure the foil is treated inanaqueous. solution of 0.05 n mercurous nitrate,

0.025 n nitricacid and 0.05 11 sodium acetate and is then physically developed in the manner described in-- Example VIII.

Due to the presence of sodium acetate in the aftertreatment bath the sensitivity is increased by a value 4.

Example XI A foil of superficially saponified cellulose acetate is sensitised with a solution of 0.2 n methoxy-l benzol diazo sodium sulphonated-4 and 0.1 n lactic acid.

The resultant photo-sensitive material is exposed for 1 second with the use of a 250 Watt high-pressure mercury vapour lamp at a distance of cms., is then treated in a solution of 0.1 n mercurous nitrate and 0.05 n nitric acid and finally physically developed as in the Example IV.

If the sensitising solution does not contain lactic acid, the sensitivity is 2.5 times lower.

In this example and in all the other examples development may be eifected in a dye-forming manner, for example, in a red colour with the use of a developer comprising ccm. of a solution containing 0.08% amino-4 phenyl amine nitrate and 5% tartaric acid in water, 1 com. of a 10% solution of AgNOs in water and 1 com. of a 2% solution of bihydroxy-l.5 naphthalene inethanol.

A suitable dye-forming developer containing mercurous nitrate is obtained for example by addition of 1 ccm. of a 10% solution of naphthol-l in ethanol to 25 ccm. of a solution containing 1 n lactic acid, 0.028 n mercurous nitrate and 008% bimethyl amino-4 phenyl amine nitrate. After physical development and bleaching of the mercury image the colour is blue.

Example XII superficially saponified cellulose-acetate is sensitised by soaking for 2 minutes with an aqueous solution of 0.4 n hydroxy-l diazo-2 methyl-6 benzol sulphonic acid-4, 0.1 n mercurous nitrate and 0.0125 11 silver nitrate.

After drying, the length of the film is exposed behind a sensitometer wedge with the use of a 125 Watt mercury vapour lamp, is then bathed for seconds in a 0.6 11 solution of sodium lactate, is washed for a short time in distilled water, and finally physically developed for 5 minutes in a developer containing 1% metol, 3.5% citric acid and 0.4% silver nitrate in water.

The sensitivity is greater by a value 8 than if subsequent to exposure and prior to physical development only a treatment with water is efiected.

What we claim is:

l. A method of producing photographic contrasts comprising the steps, exposing portions of a light-sensitive system comprising a lyophile support containing a light-sensitive compound selected from the group consisting of o-nitro-mandelonitrile and aromatic diazo compounds to decompose said compound at selected portions of said system, simultaneously contacting said light decomposition product with a Water-soluble mercurous salt and a compound selected from the group consisting of lactic acid, acetic acid and citric acid and soluble salts of said acids in the presence of moisture to form a physically intensifiable contrast, and subsequently physically developing said contrast by applying thereto a developing solution containing a reducible salt of a noble metal and a water-soluble reducing agent.

2. A method of producing photographic contrasts comprising the steps, exposing portions of a light-sensitive system comprising a lyophile support containing an aromatic diazo compound to decompose said compound at selected portions of said system, simultaneously contacting said light-decomposition product with a watersoluble mercurous salt and a compound selected from the group consisting of lactic acid, acetic acid and citric acid and soluble salts of said acids in the presence of moisture to form a physically intensifiaole contrast, and subsequently physically developing said contrast by applying thereto a developing solution containing a reducible salt of a noble metal and a water-soluble reducing agent.

3. A method of photochemically producing photographic contrasts comprising the steps, exposing portions of a light-sensitive system comprising a lyophile support containing o-nitro-mandelonitrile to decompose said compound at selected portions of said system and simultaneously contacting said light-decomposition product with a Water-soluble mercurous salt and a compound selected from the group consisting of lactic acid, acetic acid and citric acid and soluble salts of said acids in the presence of moisture to form a physically intensifiable contrast, and subsequently physically developing said contrast by applying thereto a developing solution containing a reducible salt of a noble metal and a water-soluble reducing agent.

4. A method of producing photographic contrasts comprising the steps, exposing portions of a light-sensitive system comprising a lyophile support containing a light-sensitive compound selected from the group consisting of o-nitro-rnandelonitrile and aromatic diazo compounds to decompose said compound at selected portions of said system, simultaneously cont-acting said light decomposition product with a Water-soluble mercurous salt and a soluble lactate in the presence of moisture to form a physically intensifiable contrast, and subsequently physically developing said contrast by applying thereto a developing solution containing a reducible salt of a noble metal and a Water-soluble reducing agent.

5. A method of producing photographic contrasts coniprising the steps, exposing portions of a light-sensitive system comprising a lyophile support containing a lightsensitive compound selected from the group consisting of o-nitro-mandelonitrile and aromatic diazo compounds to decompose said compound at selected portions of said system, simultaneously contacting said light dccomposition product with a water-soluble mercurous salt and a soluble citrate in. the presence of moisture to form a physically intensifiable contrast, and subsequently physically developing said contrast by applying thereto a developing solution containing a reducible salt of a noble metal and a water-soluble reducing agent.

6. A method of producing photographic contrasts comprising the steps, exposing portions of a light-sensitive system comprising a lyophile support containing a lightsensitive compound selected from the group consisting of o-nitro-mandelonitrile and aromatic diazo coinporsds to decompose said compound at selected portions of said system, simultaneously contacting said light-decomposition product with a Water-soluble mercurous salt and a soluble acetate in the presence of moisture, to form a physically intensifiable contrast, and subsequently physica ly developing said contrast by applying thereto a devcloping solution containing a reducible salt of a noble metal and a water-soluble reducing agent.

7. A method of producing photographic contrasts comprising the steps, exposing portions of a light-sensitive system comprising a lyophile support containing a lightsensitive compound selected from the group consisting of o-nitro-mandelonitrile and aromatic diazo compounds to decompose said compound at selected portions of said system, simultaneously contacting said light-decomposition product with a Water-soluble mercurous salt and a compound selected from the group consisting of lactic acid, acetic acid and citric acid and soluble salts of said acids in the presence of moisture to form a physically intcnsifiable contrast, and subsequently physically developing said contrast by applying thereto a developing solution containing a reducible salt of a noble metal and a Water-soluble reducing agent and a color-forming component to form a color contrast.

8. A method of producing photographic contrasts comprising the steps, exposing portions of a light-sensitive system comprising a lyophile support containing a lightsensitive compound selected from the group consisting of o-nitro-mandelonitrile and aromatic diazo compounds and a water-soluble mercurous salt to decompose said light sensitive compound at selected portions of said system, simultaneously contacting said light-decomposition product with moisture and a compound selected from the group consisting of citric acid, lactic acid, acetic acid and soluble salts of these acids to form a physically intensifiable contrast andsubsequcntly physically developing said contrast by applying thereto a developing solution containing a reducible salt of a noble metal and a water-soluble reducing agent.

9. A material for obtaining photographic contrasts comprising a lyophile carrier and a light-sensitive system supported by said carrier and comprising a water-soluble mercurous salt, a light sensitive compound selected from the group consisting of o-nitro-mandelonitrile and aro matic diazo compounds and a water-soluble salt selected from the group consisting of lactates, citrates and acetates.

10. A material for obtaining photographic contrasts comprising a lyophile carrier and a light-sensitive system supported by said carrier and comprising a Water-soluble mercurous salt, o-nitro-mandelonitrile and a water'sob uble salt selected from the group consisting of lactates, citrates, and acetates.

11. A material for obtaining photographic contrasts comprising a lyophile carrier and a light-sensitive system supported by said carrier and comprising a watersoluble mercurous salt, an aromatic diazo compound and a Water-soluble salt selected from the group consisting of lactates, citrates and acetates.

12. A material for obtaining photographic contrasts comprising a lyophile carrier and a light-sensitive system supported by said carrier and comprising a watersoluble mercurous salt, a light sensitive compound selected from the group consisting of o-nitro-mandelonitrile and aromatic diazo compounds and a soluble lactate.

13. A material for obtaining photographic contrasts comprising a lyophile carrier and a light-sensitive system supported by said carrier and comprising a water-soluble mercurous salt, a light sensitive compound selected from the group consisting of o nitro-mandelonitrile and aromatic diazo compounds and a soluble citrate.

14. A material for obtaining photographic contrasts comprising a lyophile carrier anda light-sensitive system supported by said carrier and comprising a water-soluble mercurous salt, a light sensitive compound selected from the group consisting of o-nitro-mandelonitrile and aromatic diazo compounds and a soluble acetate.

References Cited in the file of this patent UNITED STATES PATENTS 1,906,240 Schmidt et al. May 2, 1933 2,067,690 Alink et al. Jan. 12, 1937 2,099,297 Clement Nov. 16, 1937 2,150,834 Holst et al Mar. 14, 1939 2,183,447 Dippel et a1 Dec. 12, 1939 2,336,309 Snell et al. Dec. 7, 1943 2,442,061 Slifkin May 25, 1948 2,571,670 Bos et al. Oct. 16, 1951 2,571,671 Bos et al. Oct. 16, 1951 

1. A METHOD OF PRODUCING PHOTOGRAPHIC CONTRASTS COMPRISING THE STEPS, EXPOSING PORTIONS OF A LIGHT-SENSITIVE SYSTEM COMPRISING A LYOPHILE SUPPORT CONTAINING A LIGHT-SENSITIVE COMPOUND SELECTED FROM THE GROUP CONSISTING OF O-NITRO-MANDELONITRILE AND AROMATIC DIAZO COMPOUNDS TO DECOMPOSE SAID COMPOUND AT SELECTED PORTIONS OF SAID SYSTEM, SIMULTANEOUSLY CONTACTING SAID LIGHT DECOMPOSITION PRODUCT WITH A WATER-SLOUBLE MERCUROUS SALT AND A COMPOUND SELECTED FROM THE GROUP CONSISTING OF LACTIC ACID, ACETIC ACID AND CITRIC ACID AND SOLUBLE SALTS OF SAID ACIDS IN THE PRESENCE OF MOISTURE TO FORM A PHYSICALLY INTENSIFICALBE CONTRAST, AND SUBSEQUENTLY PHYSICALLY DEVELOPING SAID CONTRAST BY APPLYING THERETO A DEVELOPING SOLUTION CONTAINING A REDUCIBLE SALT OF A NOBLE METAL AND A WATER-SOLUBLE REDUCING AGENT. 